The present invention relates generally to universal couplers, and more particularly to a coupler permitting a predetermined amount of off-axis deflection and movement between coupled shafts, and for permitting torque transfer between the coupled shaft members.
The well known ball-and-socket coupler permits two members to be coupled together while providing for freedom of relative axial movement between the two members. The ball-and-socket coupler does not permit torque transmission between the two members, along an axis, because the two members are inherently freely rotatable with respect to one another. By equipping a ball-and-socket coupler with a threaded locking member, which locking member selectively compresses the socket about the ball, a certain amount of torque transmission is possible. However, in this type of construction the locking fit provided by the threaded locking member clamps the ball in the socket to prevent free axial movement of the two members being coupled. Such a device is illustrated in U.S. Pat. No. 1,779,057, issued Oct. 21, 1930, wherein a ball is captured within a socket and the socket is selectively clamped about the ball to provide degrees of relatively fixed adjustment of the ball with respect to the socket.
Another form of flexible coupler is shown in U.S. Pat. No. 3,940,946, issued Mar. 2, 1976. This patent discloses a universal joint for coupling two members, one member having a curved polyhedron head and the other member having a socket for receiving the curved polyhedron head with an interference fit. The polyhedron head is coated with an elastomeric material prior to forming the interference fit, to thereby permit the elastomeric material to deform under the various axial stresses encountered in use, permitting relative movement by the polyhedron head within the socket. The restrictive effect of the interference fit is thereby alleviated to permit some flexibility in relative axial movement between the head and socket.
To the extent that a universal coupler or universal joint is to be constructed free from backlash effects during torquing movements, either the dimensional tolerances between the respective head and socket must be maintained extremely critically, or some sort of cushioned interference fit must be provided. If close dimensioning tolerances are used the cost of the universal coupler increases through the need for finer machining tolerances. If a cushioned interference fit is created the cushioning material will eventually suffer degradation from wear, and the backlash effect will inevitably become more pronounced with use.
There is a need for a universal coupler having a very close dimensional fit between the head and socket member, while at the same time providing relatively free rotational coupling between the members, in a construction which the relative fit between the head and socket members will not degrade with operational use. Further, there is a need for a universal coupler wherein the relative design tolerance between the head and socket members may be relaxed so as to permit economical construction of these members, while permitting adjustment of the clearances to eliminate rotational backlash during rotational torque transmission.